This invention relates to polymer-bound metal-containing compositions, and the use of such compositions to limit the growth of viruses, bacteria, and fungi.
The potential for the presence of pathogenic bacteria and viruses in biological fluids such as saliva, tears, blood, and lymph is of significant concern as is the potential for the transfer of such microorganisms to the surfaces of medical devices (and vice versa). For these reasons, methods for minimizing the transmission of pathogens in the home and in hospitals, as well as in day-care centers, are important.
Microorganisms can be killed or rendered static by a number of physical and chemical methods. Physical methods include heat and radiation. There are a number of chemicals that have been used to limit viral, fungal, and bacterial growth. Examples include alcohols (usually, 70% by volume aqueous ethyl or isopropyl alcohol); phenol and phenol derivatives such as hexachlorophene; formaldehyde; glutaraldehyde; ethylene oxide; ether; detergents; chlorhexidine gluconate; heavy metals such as silver, copper, and mercury; organic compounds of mercury such as mercurochrome; as well as oxidizing agents such as hydrogen peroxide, iodine, hypochlorite, and chlorine.
Antibiotics, such as bacitracin, the cephalosporins, cycloserine, the penicillins, vancomycin, chloramphenicol, the erythromycins, the tetracyclines, the sulfonamides, and the aminoglycosides (such as streptomycin, neomycin, and gentamycin) have traditionally been defined as chemicals made by microorganisms that kill bacteria. Antibiotics have no effect on viruses.
Many of such treatment methods are neither permanent nor continuous. Thus, repeated treatments may be needed to restore sterility during and after use. Polymeric compositions intended for imparting a continuously antimicrobial, self-disinfecting property to surfaces or liquids are known. Typically, these involve an antimicrobial agent and a polymer in a mixture that allows leaching of the antimicrobial agent for controlled release. In some cases, the antimicrobial agent that leaches from the polymer is toxic or imparts undesirable properties to the material in the leached form. Thus, there is considerable interest in autosterile (possessing intrinsic microbicidal activity) non-leaching materials.
There are also examples of polymeric compositions that include an antimicrobial moiety covalently bonded to a polymer. Rose bengal, for example, has been covalently attached to poly(styrene), and porphyrins have been bonded to acrylates, with the resulting polymers in both cases possessing antimicrobial activity with no leaching.
Singlet oxygen is generated in neutrophils and macrophages for use in killing microorganisms of a wide variety. The xe2x80x9cphotodynamic effectxe2x80x9d is the term used to describe destruction of cells and microbes by triplet-sensitizers in the presence of oxygen and light. Singlet oxygen is believed to be the destructive agent under conditions where oxygen concentration is high and there are no reducing agents present. Singlet oxygen is a short-lived excited state of molecular oxygen. In solution, its lifetime of 1 microsecond allows it to diffuse on the order of 0.1 micron before being deactivated to triplet molecular oxygen. In the gas phase in air, the lifetime of singlet oxygen is about 1 millisecond, which allows for diffusion of up to 1 millimeter before deactivation to triplet oxygen. The combinations of certain photosensitizers, oxygen, and light have been shown to be toxic to living tissue, which is believed to be the consequence of the formation of singlet oxygen.
Thus, photosensitizing dyes, such as merocyanines and water-soluble zinc phthalocyanines, have been disclosed for use as antimicrobial agents. Surfaces coated with certain photosensitizers can be made to be autosterile. Due to the catalytic nature of the photosensitizer-oxygen reaction that generates singlet oxygen and regenerates ground-state photosensitizers, the antimicrobial activity of such coatings can be made to be essentially permanent. Additionally, certain immobilized photosensitizers have been shown to exhibit antimicrobial activity at a distance due to diffusion of singlet oxygen.
Use of photosensitizers compounded with or covalently attached to polymers to prepare substantially non-leaching autosterile materials is known. For example, various polymers that include covalently-bound porphyrin, phthalocyanine, and Rose Bengal photosensitizers are known.
U.S. Pat. No. 6,248,733 (Landgrebe et al.) discloses the use of metal-containing compounds in polymeric compositions (e.g., porous fabrics). For certain embodiments of the compounds described therein, specifically, wherein R1 includes a long chain organic group containing, e.g., 8 or 9 carbon atoms, no antimicrobial activity was observed. These findings are consistent with the theory that leaching of the metal-containing compound is required to impart antimicrobial activity.
In one aspect, the present invention provides a method for limiting the presence of a microorganism. The method includes contacting the microorganism with a polymer-bound metal-containing composition. The composition includes a compound having the following formula: 
wherein:
Z1 and Z2 each independently represent an arene nucleus, which has from 5 to 14 ring atoms;
G1 and G2 each independently represent a metal ligating group such that G1 and G2 may be contained within or pendant from at least one of Z1 and Z2;
R represents a hydrogen atom, a halogen atom, an alkyl group, an acylamino group, an alkoxy group, a sulfonamido group, an aryl group, a thiol group, an alkylthio group, an arylthio group, an alkylamino group, an arylamino group, an amino group, an alkoxycarbonyl group, an acyloxy group, a nitro group, a cyano group, an alkyl- or aryl sulfonyl group, an alkyl- or aryl sulfoxyl group, an aryloxyl group, a hydroxyl group, a thioamido, a carbamoyl group, a sulfamoyl group, a formyl group, an acyl group, a ureido group, an aryloxycarbonyl group, a silyl group, or a sulfoalkoxy group;
L1 represents a nitrogen heterocycle substituted with R1 or R2 or both R1 and R2;
R1 and R2 each independently represent a polymer-bound group, a hydrogen, a halogen atom, an alkyl group, a vinyl group, a hydroxyalkyl group, an acylamino group, an alkoxy group, a sulfonamido group, an aryl group, an alkylthio group, an alkylamino group, an alkoxycarbonyl group, an acyloxy group, an alylsulfonyl group, an alkylsulfoxyl group, an alkylcarbamoyl group, an alkylsulfamoyl group, a formyl group, an acyl group, a silyl group, or a sulfoalkoxy group; wherein at least one of R1 and R2 represents a polymer-bound group;
L2 represents a monodentate or polydentate ligand;
X represents nitrogen or a methine group;
M represents a platinum or palladium atom; and
k, m, and n are whole numbers less than or equal to 4.
In one embodiment, the polymer-bound metal-containing composition includes a compound of the following formula: 
wherein:
R1 and R2 each independently represent H or a polymer-bound group, wherein at least one of R1 and R2 is a polymer-bound group; X represents nitrogen or a methine group; and M represents a platinum or palladium atom.
In another aspect, the present invention provides a polymer-bound metal-containing compound of the following formula: 
wherein:
R1 and R2 each independently represent H or a polyurethane-bound group, wherein at least one of R1 and R2 represents a polyurethane-bound group;
X represents nitrogen or a methine group; and
M represents a platinum or palladium atom.
In still another aspect, the present invention provides a method of preparing a polymer-bound metal-containing compound that includes reacting a prepolymer or polymer with a metal-containing monomer of the following formula: 
wherein:
R1 and R2 each independently represent H or CH2OH, wherein at least one of R1 and R2 represents CH2OH;
X represents nitrogen or a methine group; and
M represents a platinum or palladium atom.
In one embodiment, the method includes reacting an isocyanate functional prepolymer or polymer with the monomer.
xe2x80x9cPolymer-boundxe2x80x9d means a group that is irreversibly attached to a polymer either through covalent bonds or steric entanglement. A polymer-bound group that is a substituent on a heterocyclic ring may be a polymer that is covalently attached to the heterocyclic ring either through a backbone atom, a side chain atom, or a terminal atom of a polymer chain. Alternatively, the polymer-bound group may be a group that is sterically entangled with a polymer chain, such as might arise by dimerization, oligomerization, or polymerization of a reactive group attached to the heterocyclic ring in the presence of a preformed polymeric matrix. Preferably, the polymer-bound group includes a polymer covalently attached to the heterocyclic ring. xe2x80x9cMetal-containing compoundxe2x80x9d means that the compound contains one or more coordinated transition metal atom, preferably platinum or palladium.
For the purposes of this invention, the terms xe2x80x9climiting the presence of a microorganismxe2x80x9d or xe2x80x9cantimicrobial activityxe2x80x9d include limiting the presence of at least one virus, at least one bacterium, at least one fungus, or a combination thereof. Limiting the presence of a microorganism includes limiting the growth of a microorganism. This term also includes inhibiting, inactivating, killing, or preventing the replication of or reducing the number of microorganisms. Different terms may be used for different microorganisms.
The terms xe2x80x9climiting the presence of a virus,xe2x80x9d xe2x80x9cinactivation of virus,xe2x80x9d xe2x80x9cviricidal activity,xe2x80x9d and xe2x80x9cviricidalxe2x80x9d as used herein refer to a reduction in the amount of virus present in a sample contacted with the composition of the present invention. These terms also refer to a reduction in the amount of virus, present in a sample contacted with the composition of this invention, that is able to enter and/or replicate in a cell. Preferably, the terms refer to at least about 50% reduction in the amount of at least one species of virus detected on a surface of the composition relative to similar compositions that do not include metal-containing compounds under the same conditions, using the test method as described in Example 4 below. More preferably, the compositions of the present invention provide at least about 75% reduction in the amount of at least one species of virus, even more preferably, at least about 90% reduction, and most preferably, at least about 99% reduction in at least one species of virus.
The term xe2x80x9climiting the presence of a fungus or a bacteriumxe2x80x9d as used herein refers to methods that employ the use of compositions of the present invention to inhibit, kill, or prevent the replication of or reduce the number of bacteria or fungi present on a surface of the composition. Preferably, the term refers to an at least about 40% reduction (as evidenced by the inhibition of growth or killing, for example) in the amount of at least one species of fungus or bacterium detected on a surface under the same conditions using the test method described in Example 5, for a composition of the present invention relative to similar compositions that do not include metal-containing compounds. For example, growth of bacteria or fungi is limited by the compositions of the present invention when disks cut from the composition preferably kill at least about 40% or more of the bacteria or fungi placed on them as evidenced by washing away the original bacteria or fungi, attempting to grow colonies on an agar surface, and observing a reduction in the number of colonies that grow in comparison to the original inoculum and a control that does not include one or more polymer-bound metal-containing compositions of the present invention. More preferably, the compositions of the present invention provide at least about 75% reduction, even more preferably, at least about 90% reduction, and most preferably, at least about 99% reduction, in the amount of at least one species of fungus or bacterium detected on a surface of the composition relative to similar compositions that do not include metal-containing compounds under the same conditions, using the test method described in Example 5 below.
An xe2x80x9ceffective amountxe2x80x9d of one or more of the metal-containing compounds of this invention refers to a concentration of polymer-bound metal-containing compound that is sufficient to limit the presence of a microorganism.
The term xe2x80x9ccontactingxe2x80x9d as used in the methods of this invention includes either physical contact of the compositions of this invention with a virus, a bacterium, or a fungus, or exposure without direct physical contact of a virus, a bacterium, or a fungus to the compositions of this invention. Without intending to limit the scope of this invention, many of the polymer-bound metal-containing compositions of this invention may form diffusible substances in the light, such as singlet oxygen, which mediate an antimicrobial effect on the virus, bacterium, or fungus. Therefore, direct physical contact may not be necessary.
The term xe2x80x9cbacteriostaticxe2x80x9d refers herein to the property of inhibiting bacterial growth but not necessarily killing the bacteria. The term xe2x80x9cbactericidalxe2x80x9d refers to killing bacteria. The term xe2x80x9cfungistaticxe2x80x9d refers herein to the property of inhibiting fungal growth but not necessarily killing the fungus. The term xe2x80x9cfungicidalxe2x80x9d refers to killing the fungus. Thus, the compositions of this invention can be either bactericidal or bacteriostatic or fungicidal or fungistatic or viricidal. Methods for limiting the presence of a bacterium and fungus include xe2x80x9ccidalxe2x80x9d (i.e., killing) activity. The term microbicidal is used to encompass the terms bactericidal, fungicidal, and viricidal.
The term xe2x80x9csubstantially non-leachingxe2x80x9d means that less than about 200 nanograms of a metal (as coordinated metal) leaches from a 113 mm2 sample (6 mm diameter disk of any thickness) of polymeric material that has been soaked in 2.0 ml biological medium (for example, Trypticase Soy Broth) for 24 hours at room temperature. Determination of the metal concentration can be performed, for example, using Inductively-coupled Plasma-Mass Spectrometry (ICP-MS) as described in the Examples. A low value of leaching for a given polymer-photosensitizer composition (as determined by testing for leaching of the appropriate metal) is consistent with a polymer-bound metal-containing composition having a low level of unbound metal-containing compound.